Methods for cleaning industrial equipment with pre-treatment

ABSTRACT

A method of cleaning equipment such as heat exchangers, evaporators, tanks and other industrial equipment using clean-in-place procedures and a pre-treatment solution prior to the conventional CIP cleaning process. The pre-treatment step improves the degree of softening of the soil, and thus facilitates its removal. The pre-treatment solution can be a strong acidic solution, a strong alkaline solution, or comprise a penetrant. A preferred strong acidic solution is an acid peroxide solution. In some embodiments, the pre-treatment may include no strong alkali or acid ingredient; rather, the penetrant provides acceptable levels of pre-treatment.

FIELD

The invention relates to cleaning of industrial equipment such asevaporators, heat exchanger and other such equipment that isconventionally cleaned using a CIP (clean-in-place) process.

BACKGROUND

In many industrial applications, such as the manufacture of foods andbeverages, hard surfaces commonly become contaminated with carbohydrate,proteinaceous, hardness soils and other soils. Such soils can arise fromthe manufacture of both liquid and solid foodstuffs. Carbohydrate soils,such as cellulosics, monosaccharides, disaccharides, oligosaccharides,starches, gums and other complex materials, when dried, can form tough,hard to remove soils, particularly when combined with other soilcomponents such as proteins, enzymes, fats, oils and others. The removalof such carbohydrate soils can be a significant problem. Similarly,other materials such as proteins, enzymes, fats and oils can also formhard to remove soil and residues.

Clean-in-place cleaning techniques are a specific cleaning regimenadapted for removing soils from the internal components of tanks, lines,pumps and other process equipment used for processing typically liquidproduct streams such as beverages, milk, juices, etc. Clean-in-placecleaning involves passing cleaning solutions through the system withoutdismantling any system components. The minimum clean-in-place techniqueinvolves passing the cleaning solution through the equipment and thenresuming normal processing. Any product contaminated by cleaner residuecan be discarded. Often clean-in-place methods involve a first rinse,the application of the cleaning solutions, a second rinse with potablewater followed by resumed operations. The process can also include anyother contacting step in which a rinse, acidic or basic functionalfluid, solvent or other cleaning component such as hot water, coldwater, etc. can be contacted with the equipment at any step during theprocess. Often the final potable water rinse is skipped in order toprevent contamination of the equipment with bacteria following thecleaning sanitizing step.

Clean-in-place processing requires a complete shutdown of the equipmentbeing cleaned, which results in lost production time. Many times, theequipment is not thoroughly cleaned, due to the large downtime needed.What is needed is an improved method for cleaning this equipment, usingthe clean-in-place process, which uses less time to thoroughly removethe soils.

SUMMARY OF THE DISCLOSURE

The invention relates to methods of cleaning equipment such as heatexchangers, evaporators, tanks and other industrial equipment usingclean-in-place procedures. The method is suitable for organic soilremoval or, more particularly, for food soil removal. Further, themethod relates to cleaning processes for removing carbohydrate andproteinaceous soils from beverage manufacturing locations using aclean-in-place method. The method includes using a pre-treatment orpre-treating step prior to the conventional cleaning process.

In one aspect, the invention is directed to a method that includespre-treating the soiled surfaces with a strong acidic solution. Aconventional clean-in-place process follows this pre-treatment step. Apreferred strong acidic solution is an acid peroxide solution. It hasbeen found that a conventional clean-in-place process using an alkalinedetergent after the strong acidic pre-treatment step providesparticularly effective results. The concentration of the activeingredients in an acidic pre-treatment solution is at least 0.3% andusually at least 0.6%.

In another aspect, the invention is directed to a method that includespre-treating the soiled surfaces with a strong alkaline solution. Aconventional clean-in-place process follows this pre-treatment step. Ithas been found that a conventional clean-in-place process using anacidic detergent after the strong alkaline pre-treatment step providesparticularly effective results.

Either of the pre-treatments, either acidic or alkaline, may include apenetrant. The addition of a penetrant improves the degree of softeningof the soil, and thus facilitates the removal of the soil. Theconcentration of acid plus peroxide in a pre-treatment solution is atleast 0.5% and usually at least 0.7%. A concentration of about 1% istypical.

In another aspect, the invention is directed to a method that includespre-treating the soiled surfaces with a penetrant, without the presenceof appreciable amounts of acid or alkaline. A conventionalclean-in-place process follows this penetrant pre-treatment step. Theconcentration of penetrant in the pre-treatment solution is at least0.25% and usually is at least 0.5%. In one particular embodiment, thepenetrant pre-treatment solution comprises approximately 0.9% of a blendof glycol ether solvents; other levels of glycol ethers as penetrantsare suitable.

In one particular embodiment, the invention is to a method of cleaningsoils from industrial equipment using a CIP process. The method includesapplying a pre-treatment solution to the soil, the solution comprisingat least 0.25 wt-% active ingredients, with the active ingredientsincluding any of an alkaline source, an acidic source, a penetrant, anoxidizer, and a builder. The method also includes recirculating a firstCIP solution through the equipment after the pre-treatment solution, theCIP solution comprising a dilute detergent and then rinsing theequipment. The pre-treatment solution can have 0.25 to 1.5 wt-% acid and0.01 to 1 wt-% oxidant, such as a peroxide. A penetrant, such as glycolether, may be present at 0.4 to 10 wt-%.

In another particular embodiment, the method includes pre-treating thesoil with a pre-treatment solution comprising at least 0.5 wt-% activeingredients, the active ingredients including any of an alkaline source,an acidic source, a penetrant, an oxidizer, a surfactant, and a builder,removing at least a portion of the penetrated soil with a dilutedetergent solution, and rinsing the equipment. In some embodiments, thepre-treatment solution includes an alkaline source and the dilutedetergent includes an acid. In other embodiments, the pre-treatmentsolution includes an acid source and the dilute detergent is basic.

The present invention includes using two different CIP solutions.

Additional details regarding pre-treatment solutions and methods ofusing pre-treatment solutions are provided below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an industrial process that includesequipment to be cleaned, CIP process equipment, and pre-treatmentequipment.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to cleaning of industrial equipmentusing a pre-treatment step in combination with clean-in-placeprocedures. Use of a pre-treatment step, in combination withconventional clean-in-place solutions and processes, provides increasedsoil removal than the conventional process alone. Additionally, use of apre-treatment step, followed by a water rinse, provided unexpectedamounts of soil removal. Use of a pre-treatment step allows the use oftraditionally incompatible chemistries.

As used herein, “weight percent”, “wt-%”, “percent by weight”, “% byweight”, and variations thereof refer to the concentration of asubstance as the weight of that substance divided by the total weight ofthe composition and multiplied by 100. It is understood that, as usedhere, “percent”, “%”, and the like are intended to be synonymous with“weight percent”, “wt-%”, etc.

As used herein, the term “about” refers to variation in the numericalquantity that can occur, for example, through typical measuring andliquid handling procedures used for making concentrates or use solutionsin the real world; through inadvertent error in these procedures;through differences in the manufacture, source, or purity of theingredients used to make the compositions or carry out the methods; andthe like. The term “about” also encompasses amounts that differ due todifferent equilibrium conditions for a composition resulting from aparticular initial mixture. Whether or not modified by the term “about”,the claims include equivalents to the quantities.

It should be noted that, as used in this specification and the appendedclaims, the singular forms “a,” “an” and “the” include plural referentsunless the content clearly dictates otherwise. Thus, for example,reference to a composition containing “a compound” includes having twoor more compounds. It should also be noted that the term “or” isgenerally employed in its sense including “and/or” unless the contentclearly dictates otherwise.

The method of the present invention applies to equipment generallycleaned using clean-in-place (i.e., CIP) cleaning procedures. Examplesof such equipment include evaporators, heat exchangers (includingtube-in-tube exchangers and plate-in-frame exchangers), heating coils(Including steam, flame or heat transfer fluid heated) re-crystalizers,pan crystalizers, spray dryers, drum dryers, and tanks. This method canbe used in generally any application where caked on soil or burned onsoil, such as proteins or carbohydrates, needs to be removed;applications include the food industry (especially dairy), brewing, oilprocessing, industrial agriculture and ethanol processing.

CIP processing is generally well-known. The process includes applying adilute solution (typically about 0.5-3%) onto the surface to be cleaned.The solution cascades across the surface (typically drains down), slowlyremoving the soil. Either new solution is re-applied to the surface, orthe same solution is recirculated and re-applied to the surface.

A typical CIP process to remove a soil (including organic, inorganic ora mixture of the two components) includes at least three steps: analkaline solution rinse, an acid solution rinse, and then a water wash.The alkaline solution softens the soils and removes the organic alkalinesoluble soils. The subsequent acid solution removes mineral soils leftbehind by the alkaline cleaning step. The strength of the alkaline andacid solutions and the duration of the cleaning steps are typicallydependent on the durability of the soil. The water rinse removes anyresidual solution and soils, and cleans the surface prior to theequipment being returned on-line. The present invention provides apre-treatment step, prior to the CIP process, which penetrates into thesoil. The penetrating materials soften the soil, act as a catalyst, orotherwise enhance the activity of the conventional CIP solution when itcontacts the soil. Thus, the pre-treatment facilitates the soil removal.

Referring now to FIG. 1, a schematic diagram of process equipment isillustrated at reference numeral 10. Process 10 includes a tank 20,which is the equipment to be cleaned. A feed line 25 supplies thevarious cleaning solutions to tank 20, and a drain line 27 removessolution from tank 20. Operably connected via appropriate pipes, valves,pumps, etc. is equipment for a CIP process, designated as referencenumeral 30. CIP process 30 includes a tank 35 for retaining the diluteCIP chemistry. Drain line 27 from tank 20 is used to recirculatesolution from tank 20 back to CIP process 30 and tank 35. Process 10also includes equipment for the pre-treatment process, designated asreference numeral 40. Pre-treatment equipment 40 includes a first tank42 and a second tank 44. When two tanks are used, generally one tank,e.g., tank 42, will contain an alkaline pre-treatment and the othertank, e.g., tank 44, will contain an acidic pre-treatment. Theappropriate pipes, valves, pumps, etc. are in place for operablyconnecting tanks 42, 44 with feed line 25 into tank 20. This set-up ofprocess 10 allows a pre-treatment to be applied to tank 20 without theuse of large amounts of additional equipment, such as piping. Additionaldetails regarding the method of cleaning tank 20 is described below.

The Pre-Treatment Solution

As described above, the pre-treatment solution or pre-treatment step isapplied to the soil prior to the application of conventional CIPchemistries. The chemistry of the pre-treatment solution is selected tofacilitate removal of the soils on the surfaces to be cleaned. Thepre-treatment solution pre-coats and penetrates into the soil, softeningthe soil. The specific chemistry used can be selected based on the soilto be removed. The chemistry used can be compatible with the CIPchemistry. In some embodiments, it is desired to have a pre-treatmentthat is incompatible with the CIP chemistry; in such instances, thepre-treatment reacts with the CIP chemistry. It has been found thatusing incompatible chemistries further increases the soil-removaleffectiveness.

The pre-treatment solution comprises at least 0.25% of activeingredients, typically at least 0.5%, preferably at least 2% and morepreferably at least 4%. By use of the term “active ingredients” what isintended is the non-inert ingredients that facilitate the softening,dissolving and removal of soil. These active ingredients include anyalkaline/base, acid, penetrant (including surfactant), builder,oxidizer, catalyst and chelant or chelating agent. In most embodiments,water is the remainder of the solution. Typically, the solution has nomore than about 15% active ingredients, preferably no more than about10%. For most applications, a concentration of about 1-10% is preferred;a concentration of about 2-5% is suitable for most applications.

Alkaline or Acidic Ingredients

The pre-treatment solution optionally and preferably includes alkalineor acidic ingredients. Examples of suitable alkaline sources includebasic salts, amines, morpholine, carbonates and silicates. Particularlypreferred alkaline sources include NaOH (sodium hydroxide), KOH(potassium hydroxide), TEA (triethanol amine), DEA (diethanol amine),and MEA (monoethanol amine), sodium metasilicate and potassium silicate.

Examples of suitable acidic sources include mineral acids (such asphosphoric acid, nitric acid, sulfuric acid), and organic acids (such aslactic acid, acetic acid, hydroxyacetic acid, citric acid, glutamicacid, glutaric acid).

The amount of alkaline or acid in the pre-treatment solution istypically at least 0.25 wt-% and no greater than 10 wt-%. Common levelsof alkaline or acid include 2 to 5 wt-% and 0.5 to 1.5 wt-%.

Penetrants

A penetrant may be present in the pre-treatment solution. The penetrantmay be combined with an alkaline or acid source in the solution, or, thepenetrant may be used without an alkaline or acid source. Preferably,the penetrant is water soluble.

Examples of suitable penetrants include alcohols, short chainethoxylated alcohols and phenol (having 1-6 ethoxylate groups). Organicsolvents are also suitable penetrants. Examples of suitable organicsolvents, for use as a penetrant, include esters, ethers, ketones,amines, and nitrated and chlorinated hydrocarbons.

Another preferred class of penetrants is ethoxylated alcohols. Examplesof ethoxylated alcohols include alky, aryl, and alkylaryl alkloxylates.These alkloxylates can be further modified by capping with chlorine-,bromine-, benzyl-, methyl-, ethyl-, propyl-, butyl- and alkyl-. Apreferred level of ethoxylated alcohols in the solution is 1 to 20 wt-%.

Another class of preferred solvents for use as penetrants is glycolethers, which are water soluble. Examples of glycol ethers includedipropylene glycol methyl ether (available under the trade designationDOWANOL DPM from Dow Chemical Co.), diethylene glycol methyl ether(available under the trade designation DOWANOL DM from Dow ChemicalCo.), and propylene glycol methyl ether (available under the tradedesignation DOWANOL PM from Dow Chemical Co.). A preferred level ofglycol ether in the solution is 0.5 to 20 wt-%.

Surfactants also are a suitable penetrant for use in the pre-treatmentsolution. Examples of suitable surfactants include nonionic, cationic,and anionic surfactants. Nonionic surfactants are preferred. Nonionicsurfactants improve soil removal and can reduce the contact angle of thesolution on the surface being treated. Examples of suitable nonionicsurfactants include alkyl-, aryl-, and arylalkyl-, alkoxylates,alkylpolyglycosides and their derivatives, amines and their derivatives,and amides and their derivatives. Additional useful nonionic surfactantsinclude those having a polyalkylene oxide polymer as a portion of thesurfactant molecule. Such nonionic surfactants include, for example,chlorine-, benzyl-, methyl-, ethyl-, propyl-, butyl- and other likealkyl-capped polyoxyethylene and/or polyoxypropylene glycol ethers offatty alcohols; polyalkylene oxide free nonionics such as alkylpolyglycosides; sorbitan and sucrose esters and their ethoxylates;alkoxylated ethylene diamine; carboxylic acid esters such as glycerolesters, polyoxyethylene esters, ethoxylated and glycol esters of fattyacids, and the like; carboxylic amides such as diethanolaminecondensates, monoalkanolamine condensates, polyoxyethylene fatty acidamides, and the like; and ethoxylated amines and ether amines and otherlike nonionic compounds. Silicone surfactants can also be used.

Additional suitable nonionic surfactants having a polyalkylene oxidepolymer portion include nonionic surfactants of C6-C24 alcoholethoxylates having 1 to about 20 ethylene oxide groups; C6-C24alkylphenol ethoxylates having 1 to about 100 ethylene oxide groups;C6-C24 alkylpolyglycosides having 1 to about 20 glycoside groups; C6-C24fatty acid ester ethoxylates, propoxylates or glycerides; and C4-C24mono or dialkanolamides.

If a surfactant is used as a penetrant, the amount of surfactant in thepre-treatment solution is typically at least 0.25% and no greater than10 wt-%. Common levels of surfactant include 0.4 to 8 wt-%, and 1 to 4wt-%.

Overall, when an alkaline or acid source is present, the amount ofpenetrant in the pre-treatment solution is typically at least 0.2 wt-%and no greater than 2.5 wt-%. Common levels of penetrant, when analkaline or acid source is present, include 0.4-2 wt-%; 1-2 wt-% ispreferred. The amount of penetrant, in relation to any alkaline or acidsource when present, is generally 1:1 to 1:5.

For pre-treatment solutions without an alkaline or acid source, theamount of penetrant in the solution is at least 0.05 wt-% and no greaterthan 50%. Typically, the level is 0.1 to 25 wt-%. Common levels ofpenetrant include 0.5 to 10 wt-%, and 1 to 5 wt-%.

Oxidizers

Acidic solutions may include an oxidizing agent or an oxidizer, such asa peroxide or peroxyacid. The resulting solution is very effectiveagainst protein soils. Further, reaction of these oxygen compounds withthe soil, especially when combined with an alkaline source, createsvigorous mechanical action on and within the soil, which enhancesremoval of the soil beyond that caused by the chemical action.

Suitable ingredients are oxidants such as chlorites, bromine, bromates,bromine monochloride, iodine, iodine monochloride, iodates,permanganates, nitrates, borates, perborates, and gaseous oxidants suchas ozone, oxygen, chlorine dioxide, chlorine, sulfur dioxide. Peroxygencompounds, which include peroxides and various percarboxylic acids,including percarbonates, are suitable. Typical peroxygen compoundsinclude hydrogen peroxide (H₂O₂), peracetic acid, a persulphate, or apercarbonate.

The amount of oxidant in the pre-treatment solution is typically atleast 0.01 wt-% and no greater than 1 wt-%. Common levels of oxidant are0.01 to 0.25 wt-%; 0.05 wt-% is a particularly suitable and commonlevel. Suitable levels of oxidant, in relation to any acid source, aregenerally 2:1 to 1:2000. Common levels are 1:2 to 1:100, more common1:20 to 1:50. Solutions of 0.25 wt-% to 10 wt-% phosphoric acid with50-5000 ppm (0.005 wt-% to 0.5 wt-%) hydrogen peroxide are particularlysuitable. An example pre-treatment solution includes 0.75 wt-%phosphoric acid and 500 ppm (0.05 wt-%) hydrogen peroxide, which is a1:15 ratio of oxidant:acid.

Builders

The pre-treatment solution preferably includes a builder. Buildersinclude chelating agents (chelators), sequestering agents(sequestrants), detergent builders, and the like. The builder oftenstabilizes the composition or solution. Examples of builders includephosphonic acids and phosphonates, phosphates, aminocarboxylates andtheir derivatives, pyrophosphates, polyphosphates, ethylenediamene andethylenetriamene derivatives, hydroxyacids, and mono-, di-, andtri-carboxylates and their corresponding acids. Other builders includealuminosilicates, nitroloacetates and their derivatives, and mixturesthereof. Still other builders include aminocarboxylates, including saltsof ethylenediaminetetraacetic acid (EDTA),hydroxyethylenediaminetetraacetic acid (HEDTA), anddiethylenetriaminepentaacetic acid. Preferred builders are watersoluble.

Particularly preferred builders include EDTA (including tetra sodiumEDTA), TKPP (tripotassium polyphosphate), PAA (polyacrylic acid) and itssalts, phosphonobutane carboxylic acid, and sodium gluconate.

The amount of builder in the pre-treatment solution, if present, istypically at least 0.25 wt-% and no greater than 5 wt-%. Common levelsof builder include 0.5 to 1.0 wt-% and 1 wt-% to 2.5 wt-%.

Methods of Pre-Treating

The method of the present invention is directed to applying thepre-treatment solution to the surface to be cleaned, prior to aconventional CIP process. The resulting CIP process requires less stepsand/or less time for each step. For example, a conventional CIP processincludes five steps after an initial water rinse: a conventionalalkaline (NaOH) wash to remove soil, an interim rinse, a conventionalacid wash to remove minerals and scale, a water rinse, and aconventional sanitizing step. This process can be replaced with athree-step process after the initial water rinse: an acidicpre-treatment step, a conventional alkaline wash, and a water rinse.Alternately, the three-step process can be: an alkaline pre-treatmentstep, a conventional acidic wash, and a water rinse. By using such aprocess, an interim rinse is not needed, as the reaction between theacid and base in separate steps is desired.

By using either of the two pre-treatment processes described immediatelyabove, the amount of water used in the overall cleaning process withpre-treatment is reduced by about 30% compared to the conventionalfive-step process. The amount of time for the overall process withpre-treatment is reduced by about 30% compared to the conventionalfive-step process. The specific number of steps, the water usage, or theprocessing time reduced will depend on the concentration and chemistryof the pre-treatment solution.

Referring again to FIG. 1, pre-treatment solution is stored at theequipment designated as 40. In this process 10, tank 42 holds analkaline pre-treatment solution and tank 44 holds an acidicpre-treatment solution that includes peroxide.

To clean 20, tank 20 and its connection lines are drained of any productthat may be present. A water rinse may be included to remove anyresidual product. In one embodiment, alkaline pre-treatment solutionfrom tank 42 is pumped via piping and feed line 25 into tank 20.Conventional CIP application equipment, such as a spray head, appliesthe pre-treatment solution onto the interior surface of tank 20. Thepre-treatment solution cascades or otherwise flows down the surface oftank 20, softening the soil. A second application of pre-treatmentsolution may be applied, although this is not generally needed.

After application and draining of the pre-treatment solution, aconventional CIP process, using the detergent from process 30 and tank35, is performed. The CIP detergent may be acidic or alkaline. Detergentfrom tank 35 is recirculated through tank 20 via feed line 25, returnline 27, and other appropriate piping.

In another embodiment, a pre-treatment solution containing hydrogenperoxide from tank 44 is pumped via piping and feed line 25 into tank20. After application and draining of the peroxide pre-treatmentsolution, a conventional CIP process, using an alkaline detergent suchas sodium hydroxide, from process 30 and tank 35, is performed. Thesodium hydroxide activates any residual peroxide on the walls of tank20.

Various generic examples of suitable pre-treatment steps are providedbelow.

In one particular example, an alkaline pre-treatment solution of 10 wt-%NaOH is sprayed onto the interior surfaces of a holding tank and allowedto drain. After about 20 minutes, the CIP process, having a 1% acidicsolution, is initiated.

In a second particular example, an acidic pre-treatment solution of 1wt-% phosphoric acid is circulated onto the interior surfaces of aplate-in-frame heat exchanger. The solution includes 0.1 wt-% H₂O₂. Theacid, together with the peroxide, provides an effervescence effect,providing mechanical action to help soften and remove the soil. Theperoxide is also catalytically activated by a subsequent conventionalalkaline CIP solution which causes further effervescence and soilremoval.

In a third particular example, an acidic pre-treatment solution, havingabout 1.0 wt-% mineral acids and 1.0 wt-% solvent penetrant, iscirculated onto the heat exchanging surfaces of an evaporator anddrained from the surface. After about 20 minutes, the CIP process isinitiated. A conventional alkaline wash, approx. 0.5 wt-% active NaOH,is fed into the evaporator. The alkaline reacts with any acidic residue,generating heat and mechanical action furthering the removal of thesoil.

EXAMPLES Example 1

Test Procedure

Solid milk pellets were prepared by mixing 3 grams of dry milk power and3 grams of soil. The resulting mix was pressed in a die for 30 secondsat 10,000 lb, and then more pressure was added to again apply 10,000 lbfor 30 additional seconds. The pellets were placed in screens andimmersed in the pre-treatment solutions, described below, for 5 minutes,removed, and then drained for 5 minutes. The screen and dried pelletswere placed in a beaker of 0.5 wt-% NaOH at 120° F. (The test designatedas “None” had no pre-treatment step; the test designated as “None *” hadno pre-treatment step and used a 3.0% NaOH cleaning at 120° F., ratherthan the 0.5% NaOH). The beakers were placed on a hot plate set to 49°C. (approx. 120° F.) with large stir bars rotating at 350 rpm. After 30minutes, the screen and pellets were removed from the cleaning solutionand gently immersed in and removed from deionized water five times, andthen dried overnight in a 50° C. oven. The results of the testing arebelow.

Pre-Treatment 1

A 10 wt-% solution of active NaOH was prepared and used as apre-treatment. The pre-treatment had 100,000 ppm sodium hydroxide (analkaline cleaner).

Pre-Treatment 2

A pre-treatment solution was prepared having 1360 ppm tetra sodium EDTA(a builder and/or chelant), 3000 ppm sodium gluconate (a builder and/orchelant), 2400 ppm potassium silicate (an alkaline cleaner), 7000 ppmalkyl polyglycoside (a surfactant), and 4200 ppm potassium hydroxide (analkaline cleaner). This Pre-Treatment 2 had 3.66% alkaline, 0.43%builder/chelant, and 0.7% surfactant, providing 4.79% activeingredients.

Pre-Treatment 3

A pre-treatment solution was prepared having 41550 ppm polycarboxylatedalcohol ethoxylate (a surfactant), 9540 ppm octyl amine oxide (asurfactant), 25500 ppm alkyl polyglycoside (a surfactant), and 4150 ppm2-ethylhexanol ethoxylate (a penetrant). This Pre-Treatment 3 had 0.4%penetrant and 7.6% surfactant, providing 8% active ingredients.

Pre-Treatment 4

A pre-treatment solution was prepared having 1600 pm potassium hydroxide(an alkaline cleaner), 9465 ppm sodium hydroxide (an alkaline cleaner),18500 ppm polyacrylic acid (a builder and/or chelant), and 4625 ppmphosphonobutane tricarboxylic acid (a builder and/or chelant). ThisPre-Treatment 4 had 1.10% alkaline and 2.3% builder/chelant, providing2.9% active ingredients.

screen + pellet screen + pellet wt, wt, pellet wt pellet wtPre-Treatment Screen wt before clean after clean before after clean % wtloss of solution (g) (g) (g) clean (g) (g) pellet 1 18.23 23.93 22.595.70 4.36 23.51% 1 18.20 23.86 22.52 5.66 4.32 23.67% 2 18.23 23.9122.54 5.68 4.31 24.12% 2 18.02 23.34 22.08 5.32 4.06 23.68% 3 19.2424.70 22.14 5.46 2.90 46.89% 3 18.06 23.67 21.19 5.61 3.13 44.21% 417.95 23.50 20.09 5.55 2.14 61.44% 4 18.22 23.90 21.69 5.68 3.47 38.91%None 19.16 24.81 23.22 5.65 4.06 28.14% None 13.47 18.76 17.22 5.29 3.7529.11%  None* 19.27 25.01 24.14 5.74 4.87 15.16%  None* 18.15 23.8223.02 5.67 4.87 14.11%

The results show both consistency within the cleaning processes anddifferences when comparing the methods. The results indicate that lowerlevels of NaOH are better than higher levels, and that pre-treatmentsolutions 3 and 4 are superior to pre-treatment solutions 1 and 2. Thisdifference, however, may be due to the test procedure used. Tests 1 and2 were done on one hot plate whereas tests 3 and 4 were done on a secondhot plate. It is possible that these two hot plates were not equal atmaintaining the 120° F. temperature.

A drastic difference was seen between the duplicate tests (i.e., 61% and39% for solution 4); it is possible that one of the pellets had a crackin it, providing a weak location for the pellet to break. The highexposed surface area would result in an increase rate if disintegration.

The tests were rerun on the same hotplate in an attempt to determine ifthere was any inconsistency between temperature control of thehotplates. The results are provided in the table below, under the columndesignated “% wt loss of pellet with pre-treat”.

As an alternative, and comparative method, 1 gram of the Pre-treatmentsolution were added to 315 grams of the 0.5% NaOH cleaning solution.Thus, rather than applying the pre-treatment chemistry as a separatestep, the pre-treatment chemistry was added to the cleaning solution.The results are provided in the table below, under the column designated“% wt loss of pellet without pre-treat”.

% wt loss of pellet % wt loss of pellet Pre-treatment with pre-treatwithout pre-treat 1 22.16% 36.92% 2 23.90% 37.39% 3 41.96% 34.01% 450.17% 31.95%

The results indicate that eliminating the separate pre-treatment stepand adding the chemicals directly to the cleaning solution increased theperformance of the two less effective solutions (1—10% NaOH; 2—10%KX-3108) and decreased the performance of the two more effectivesolutions (3—10% Quadexx 400; 4—10% Quadexx 500). All of these resultswere better than if no pre-treatment was present (which provided pelletloss of about 29%).

Example 2

Test Procedure

Soiled stainless steel test panels, having soil on one side, wereprepared by drying a mixture of mashed corn solids onto one side of thepanel in an oven at 120° C. for 4 hours. The soiled panels were thencleaned as described below.

For Test (I), with the pre-treatment step, 800 grams of Pre-Treatmentsolution 5 were placed in a 1000 ml beaker. It had been determined thatapproximately 1 gram of the pre-treatment solution contacted andremained on the soiled panel. After a brief dip in the pre-treatment,the panels were hung for 5 minutes in ambient conditions. The driedpanels were then placed in a 1000 ml beaker which had 750 g of 40° C.water with the soil side down. After 30 minutes, the panels were gentlyimmersed in and removed from deionized water five times, and the panelswere then dried. The results of the testing are below.

For Test (II), the test panels were not pre-treated, but were cleaned in750 g of 40° C. water with 1 g Pre-Treatment 5 added to the water.

For Test (III) the test panels were not pre-treated, but were cleaned in750 g of 40° C. water.

Pre-Treatment 5

A pre-treatment solution was prepared having 400 ppm tetra sodium EDTA(a builder and/or chelant), 4500 ppm tri potassium polyphosphate (abuilder and/or chelant), 3852 ppm potassium hydroxide (an alkalinecleaner), 3000 ppm polyethylene phenol ether phosphate (a surfactant),1000 ppm sodium metasilicate (an alkaline cleaner), 9000 ppm ethyleneglycol monobutyl ether (a penetrant), and 2400 ppm sodium xylenesulfonate (a surfactant). This Pre-Treatment 5 had 0.5% alkaline, 0.5%builder/chelant, 0.5% surfactant, and 0.9% penetrant, providing 2.4%active ingredients.

Test Method average % soil removed I 99.12% (average of three tests) II14.14% (average of three tests) III 14.12% (average of two tests)

The results above show that merely adding the pre-treatment chemistry tothe wash solution, does not improve the soil removal from the testpanels. Rather, separated and step-wise application of the pre-treatmentsolution and the wash solution provides improved soil removal.

The invention has been described with reference to various specific andpreferred embodiments and techniques. However, it should be understoodthat many variations and modifications may be made while remainingwithin the spirit and scope of the invention.

1. A method of cleaning soils from industrial equipment having a heatexchanger using a CIP process, the method comprising: (a) applying anacidic pre-treatment solution to the soil, the solution comprising 0.25to 1.5 wt. % acid; 0.01 to 1 wt. % oxidant; and 0.05 to 10 wt. % of apenetrant selected from the group consisting of alcohols, short chainethoxylated alcohols, phenol, organic solvents, ethoxylated alcohols,glycol ethers, and surfactants; (b) allowing the pre-treatment solutionto partially remain on the soil for a period of time sufficient tofacilitate soil removal; (c) circulating a first heated solution throughthe equipment, the solution comprising about 0.5 wt. % of an alkalinedetergent comprising NaOH; wherein there is not a rinse step betweenapplying the pre-treatment solution and applying the first solution; and(d) rinsing the equipment.
 2. The method according to claim 1, whereinthe pre-treatment solution comprises: (a) 0.25 to 1.5 wt-% acid selectedfrom the group consisting of phosphoric acid, nitric acid, sulfuricacid, lactic acid, acetic acid, hydroxyacetic acid and citric acid; and(b) 0.01 to 1 wt-% oxidant comprising a peroxygen compound.
 3. Themethod according to claim 2, wherein the peroxygen compound is presentat a level of 0.05 to 0.5 wt-%.
 4. The method according to claim 1,wherein the pre-treatment solution comprises 0.25 to 1.5 wt-% acid and0.01 to 1 wt-% oxidant.
 5. A method of cleaning soil from industrialequipment having a heat exchanger using a CIP process, the methodcomprising: (a) pre-treating the soil with a pre-treatment solutioncomprising at least 0.5 wt-% active ingredients, the active ingredientsselected from the group consisting of an alkaline source, a penetrant,an oxidizer, a surfactant, a builder and mixtures thereof; andimmediately thereafter (b) removing at least a portion of thepre-treated soil with a dilute acidic detergent solution; wherein thereis a chemical reaction between the pre-treatment solution and the dilutedetergent solution, and there is not a rinse step between applying thepre-treatment solution and applying the dilute detergent solution; and(c) rinsing the equipment.
 6. A method of cleaning soils from industrialequipment having a heat exchanger using a CIP process, the methodcomprising: (a) applying a pre-treatment solution to the soil, thesolution comprising 0.25 to 1.5 wt. % acid; 0.01 to 1 wt. % oxidant; and0.05 to 10 wt. % penetrant selected from the group consisting ofalcohols, short chain ethoxylated alcohols, phenol, organic solvents,ethoxylated alcohols, glycol ethers, and surfactants; (b) allowing thepre-treatment solution to partially remain on the soil for a period oftime sufficient to facilitate soil removal; (c) circulating a firstheated solution through the equipment after the pre-treatment solution,the solution comprising a dilute detergent; wherein there is not a rinsestep between applying the pre-treatment solution and applying the firstsolution; and (d) circulating a second CIP solution through theequipment after the first solution; and then (e) rinsing the equipment.7. The method according to claim 6, wherein the step of applying apre-treatment solution comprises: (a) applying a pre-treatment solutioncomprising 0.25 to 1.5 wt-% acid and 0.01 to 1 wt-% oxidant.
 8. Themethod according to claim 7, wherein the step of applying apre-treatment solution comprises: (a) applying a pre-treatment solutioncomprising 0.25 to 1.5 wt-% acid and 0.05 to 0.5 wt-% oxidant.
 9. Themethod according to claim 7, wherein the oxidant is a peroxide.
 10. Themethod according to claim 6, wherein the pre-treatment solution isacidic and the first solution is alkaline.